Band, tape, or strip type flat yarns are known, for example, in the form of unreinforced, so-called "Lurex".RTM. yarns having a rectangular cross-section. However, the invention is not limited to this type of yarns. Rather, yarns with a round cross-section having a twist or no twist at all can also be handled in accordance with the present teaching. Even highly twisted twines can be handled as taught herein.
The use of yarns of the above type, including highly twisted twines, in shuttleless looms has been subject to substantial difficulties in practice because, depending on the yarn characteristic, the take-off point of the yarn from the coiled yarn supply has a tendency to travel in an uncontrolled manner back and forth on the surface of the coiled yarn winding. Such undesirable travel or excursion of the take-off point from an ideal position or location, resulted in substantially reduced operational speeds of the loom, it caused more frequent thread breaking, and the resulting fabrics frequently had quality reducing characteristics. Particular difficulties have been encountered when using non-reinforced Lurex.RTM. yarns on shuttleless looms because this type yarns is pulled off the coiled yarn supply in a so-called "overhead" fashion, namely over a flange of the flanged or disk spool holding the coiled yarn supply. Conventionally, the disk spool is stationary, and the yarn is pulled off over the flange so that there is a tendency of twisting the yarn as it is being pulled off. This twisting even increases as the supply on the disk spool decreases. Such a twisting under tension is undesirable because when the tension is released, the yarn has a tendency to form undesirable loops. In the course of the withdrawal of the yarn from the supply, the twisting accumulates to such an extent that even under tension, that is while the yarn is still being withdrawn, loops can be formed. These loops can get stuck in the first thread brake downstream of the disk spool, whereby even more tension is applied to the thread. The increased tension in turn can either cause a permanent stretching of the thread which results in a reduced cross-section of the thread, or the thread may even break. Both situations are undesirable. The reduced crosssection portions in a thread reduce the quality of the fabric and the breaking of the thread in the thread brake causes a shut-down of the loom, which in turn leads to weaving faults because the thread must be tied again. Such weaving faults are especially visible in fabrics having a high proportion of weft threads of the "Lurex".RTM. type. The weaving faults are even worse where all the weft threads are of the Lurex.RTM. type. As a result, the manufacture of so-called "Lurex".RTM. fabrics is subject to a large proportion of second quality goods. This problem can be solved only by reducing the number of shut-downs of the loom, in other words, by assuring a smooth loom run.
Another problem encountered in the use of Lurex.RTM. yarns as weft threads of a woven fabric, is caused by the high elasticity of such yarns or threads. Even a small retarding of such threads as they are being pulled over the flange of the disk supply spool, causes such a stretching that a change in the finished fabric becomes noticeable, for example, in the form of a so-called thin spot or in the form of color variations. These fabric faults can even be caused when the thread is taken out of a thread layer directly in contact with the flange of the spool. These faults can also occur when a loop in the thread causes a temporary snagging of the thread advance in the thread brake.
The above discussed problems become more and more pronounced as the quantity of thread on the supply spool is being reduced in the course of the weaving process. Stated differently, the smaller the diameter of the thread supply on the supply spool, the more layers must be pulled off per unit of time so that the unwinding r.p.m. of the thread being pulled off the supply spool increases. Thus, loop formations, snagging, and thread breaking increase as the quantity of thread on the supply spool decreases. The effects are directly visible as weaving faults in the fabric. These faults reduce the quality of the goods, resulting in "seconds".
The overall appearance of a Lurex.RTM. fabric is also greatly affected by so-called "rotation points" which are caused by the overhead withdrawal of the Lurex .RTM. weft thread from the supply spool. In order to avoid all the above mentioned problems it is highly desirable that Lurex.RTM. weft threads can be withdrawn from their supply spool substantially without any twisting.
Permitting the supply spool to freely rotate in response to pulling the weft thread off in the axial direction, rather than pulling it off a stationary supply spool, has also not solved the above problems, because the synchronization of the rotation of the supply spool with the rotation of an intermediate weft thread storage device is virtually impossible, especially in high speed looms where the acceleration and deceleration of the supply spool cannot be controlled by simply pulling off the weft thread from a freely rotatable supply spool.
Even where the pulling-off direction or unwinding is perpendicular to the rotational direction of the supply spool, the above mentioned problems could not be solved heretofore because of synchronization problems between the spool drive or rotation and the drawing or pulling-off. Accordingly, heretofore, the fine control of the pulled-off yarn, that is necessary for the desired compensation, has not been achieved.